Conventionally, a damper device arranged in a fluid passage of a high-pressure fuel pump, for example, is known as this type of pulsation absorbing device (hereinafter, referred to as the conventional technique. See, for example, Patent Document 1). In the conventional technique, the damper device absorbs pulsation of pressure of the fuel discharged from the high-pressure fuel pump. This decreases the pulsation amplitude of the fuel pressure, thus stabilizing the fuel injection amount.
As shown in FIG. 4A, the damper device according to the conventional technique includes a first diaphragm 50, a second diaphragm 55, a first support member 60, which supports the first diaphragm 50 from below, and a second support member 65, which supports the second diaphragm 55 from above. The first diaphragm 50 is formed by a thin metal plate and has a periphery 51 and a middle section 52, which is recessed downward with respect to the periphery 51. The first diaphragm 50 has a dish-like shape. The second diaphragm 55 is also formed by a thin metal plate and has a periphery 56 and a middle section 57, which is recessed upward with respect to the periphery 56. The second diaphragm 55 has a dish-like shape.
The periphery 51 of the first diaphragm 50 and the periphery 56 of the second diaphragm 55 are stacked on each other. The periphery 51 and the periphery 56 are clamped by a first clamping portion 61 of the first support member 60 and a second clamping portion 66 of the second support member 65 in the vertical direction. The thickness of each of the first clamping portion 61 and the second clamping portion 66 is greater than the thickness of the periphery 51 and the periphery 56. The first clamping portion 61 and the second clamping portion 66 both have a uniform length at any radial position.
The periphery 51 of the first diaphragm 50, the periphery 56 of the second diaphragm 55, the first clamping portion 61, and the second clamping portion 66 are joined together by laser welding over the entire circumferences of the peripheries and clamping portions. Specifically, as shown in FIG. 4B, the four components, which are the periphery 51 of the first diaphragm 50, the periphery 56 of the second diaphragm 55, the first clamping portion 61, and the second clamping portion 66, are stacked on one another. In this state, a laser beam 70 is radiated in the direction perpendicular to the end faces of the components. Edge welding is continuously performed over the entire circumferences of the peripheries 51, 56 and the first and second clamping portions 61, 66 to seal and join the components together. At this time, as represented by the cross-hatched area in FIG. 4B, the diameter d of the end face of a welding region 71 is smaller than the thickness t, which is the sum of the thicknesses of the respective end faces of the periphery 51 of the first diaphragm 50, the periphery 56 of the second diaphragm 55, the first clamping portion 61, and the second clamping portion 66. The diameter of the welding region 71 decreases toward the inner side from the end face of the welding region 71. The welding region 71 is thus exposed in neither the surface of the first clamping portion 61 nor the surface of the second clamping portion 66.
As a result, the extent to which the welding proceeds inward from the end face of the welding region 71, or the amount of penetration, cannot be checked. Even if the end face of the welding region 71 is small, the inward distance of the welding region 71 is not necessarily small. Likewise, even if the end face of the welding region 71 is great, the inward distance of the welding region 71 is not necessarily great. These facts may cause insufficient welding or excessive welding, hampering achievement of an expected welding result. Essential performance of the damper device may thus not be ensured sufficiently. Also, since the conventional welding method adjusts the amount of heat input empirically, maintaining a uniform amount of penetration is difficult.